Access modes of a current wireless communications system may be mainly classified into two types: scheduling access and contention access. The scheduling access is generally applied to authorized frequency bands, that is, some charging frequency bands, for example, various cellular networks such as a Global System for Mobile Communications (GSM for short), a Universal Mobile Telecommunications System (UMTS for short), Worldwide Interoperability for Microwave Access (WiMAX for short), and Long Term Evolution (LTE for short). The contention access generally operates on non-authorized frequency bands, that is, some free frequency bands, for example, Wireless Local Area Networks (WLAN for short). Because a contention access mechanism introduces a large quantity of delays and collisions, a WLAN system not an efficient system. Especially, when a quantity of terminals that request to access the system or have accessed the system is growing, the busyness of the system also increases drastically. To resolve this problem, existing scheduling access may be introduced based on a contention access mode in the WLAN system, and a station (STA) or an access point is instructed, according to an actual situation, to switch between contention access and scheduling access. However, this solution supports only full-band use, that is, either contention access is used on all frequency bands or scheduling access is used on all frequency bands; moreover, the scheduling access mode is based on signaling design of contention access. Therefore, overheads and flexibility are inevitably limited.